Two phase fluid heat exchanger



1964 R. D. KUERSTON 3,

TWO PHASE FLUID HEAT EXCHANGER Filed Oct. 7, 1963 3 Sheets-Sheet 1 r W 2 3| 32 33 2s 9 2| WA g i 3a 29 0 3e 37 r 34 3 II 8 l6 I7 uJ I Q a: I 2E 40 n. u.| (I) I I I I I I I 52 I 4| I Cc I 42 E i w V) Di 2 :5 Q u] (I) IINVENTOR.

R. D. KUERSTON BY 3 I A TTOR/VE KS Nov. 24, 1964 R. D. KUERSTON 3,153,010

TWO PHASE FLUID HEAT EXCHANGER Filed Oct. '7, 1963 3 Sheets-Sheet 2 q 43 4e 68 g 46 g /\V 47 6o 47 I a INVENTOR.

R. D. KUERSTON FIG. 2

A TTORNE VS Nov. 24, 1964 R. D. KUERSTON 3,158,010

TWO PHASE FLUID HEAT EXCHANGER Filed Oct. 7, 1963 3 Sheets-Sheet 5 INVENTOR.

R. D. KUERSTON BY 1 FIG. 3 W

ATTORNEYS United States Patent 3,153,010 TW't) PHASE FLUKE) HEAT EXHANGER Richard D. Kuerston, Bartlesviile, Glrltn, assignor to Phillips Petroleum Company, a corporation of Delaware Filed Get. 7, 1963, Ser. No. 314,343 5 Claims. (Cl. 62525) the flashed liquid and the flashed vapors, and passing a substantially uniform concentration of the flashed liquid and flashed vapors into a plurality of flow paths.

In the liquefaction of natural gas by low temperature refrigeration for the production of liquefied natural gas or for recovery of gaseous helium therefrom, it is desirable in some instances to reduce the pressure on the liquefied gases before the separatedliquids are passed through a heat exchanger in order to have the liquefied gases at a pressure at which substantially all of the liquefied gases will be vaporized by passage through the heat exchanger. When the pressure is reduced, flashing occurs, and it is diflicult to pass a uniform concentration of the resulting two phase fluid into the various passages of the heat exchanger. If most of the flashed liquid is al lowed to pass through some of the passages and the flashed vapor is allowed to pass through the other passages, the amount of liquid vaporized will be decreased, resulting in less heat being transferred as well as an unequal distribution of the heat. For a maximum transfer of heat, it is desirable for a uniform concentration of the various constituents of the fluid to pass into each of the passages in the heat exchanger.

It has been discovered that these difficulties can be overcome by separating the two phase fluid into a liquid portion and a vapor portion, introducing a substantially equal portion of the liquid portion into each of the plurality of flow paths through the heat exchanger, and introducing substantially equal portions of the vapor portion into each of the plurality of flow paths. Systems which have been proposed in accordance with this discovery have been primarily directed to distributing a two phase fluid through a plurality of tubular passageways,.for example, through the tubes of a shell and tube indirect heat exchanger. However, the problems of two phase fluid distribution are also encountered,'and are even more troublesome, when the two phase fluid is passed through the shell and around the tubes, particularly when the heat exchanger is of the wrapped bundle or wound tube type.

In accordance with the invention there is provided means for separating the two phase fluid into a liquid component and a vapor component in combination with means for introducing the vapor component into the shell section of the heat exchanger at one or more locations, and means for distributing the liquid component across the upper portion of the tube bundle in such a manner as to provide substantially uniform horizontal distribution of ice the liquid component in the spaces between the tubes at any given level in the length of the tube bundle.

Accordingly it is an object of the invention to provide method and means for obtaining a substantially uniform horizontal distribution of a two phase fluid in the space outside of the tubes in a heat exchanger tube bundle. Another object of the invention is to provide maximum transfer of heat in a heat exchanger. Yet another object of the invention is to provide for an equal heat transfer with a plurality of flow paths.

Other aspects, objects, and advantages of the invention will become apparent to those skilled in the art from a study of the disclosure, the drawing and the appended claims to the invention.

In the drawingsFIGURE 1 is a diagrammatic representation of a low temperature refrigeration separation process embodying the invention; FIGURE 2 is an elevation view of one embodiment of apparatus for carrying out the invention; and FIGURE 3 is an elevation view of another apparatus suitable for carrying out the invention.

While the invention is applicable to various processes for liquefying a portion or all of a gas feed stream, for purposes of illustration the invention will be described in terms of a process for the recovery of helium from a natural gas stream. It is equally applicable to a process for substantially complete liquefaction of natural gas and also for liquefaction of air, hydrogen, ammonia, chlorine, etc.

Referring now to the drawing in detail and to FIGURE 1 in particular, natural gas containing hydrocarbonsnitrogen, and helium is passed through line 11 into and through parallel flow paths 12. and 13 of indirect heat exchangers 14 and 15, respectively, wherein the gas is substantially cooled. The thus cooled gas from flow paths 12 and 13 is passed through line 16, which can contain expansion valve 17, into a phase separator 18. The gas can be partially or totally liquefied in passing through flow paths 12 and 13 or upon the expansion of the gas when passed through expansion valve 17. A valve 19 can be positioned in line 11 and manipulated by a pressure recorder controller 20 responsive to the pressure of the gas in line 11 downstream of valve 19 to maintain such pressure substantially constant.

The vapors from phase separator 18 are withdrawn through line 21 and passed to a separation zone 22. wherein a further separation can be made if desired. Separation zone 22 can be any suitable means, such as, for example, a series of heat exchangers and liquid gas separators. The details of suitable means for separation zone 22 in a helium recovery system areset forth in copending application Serial No. 218,985, filed August 23, 1962, by L. G. Kitchen. Exemplary of such further process, a crude helium stream, a low B.t.u. gas, and a residue gas can be obtained in separation zone 22. The crude helium stream is passed through line 23 into and through flow path 24 of indirect heat exchanger 14 wherein the crude helium stream is passed in indirect heat exchanging relationship with additional natural gas passing through flow path 12. The warmed crude helium stream passes from flow path 24 into line 25 and can be withdrawn from the system. A valve 26 can be positioned in line 25 and manipulated by a pressure recorder controller 27 to maintain the pressure in line 25 upstream of valve 26 substantially constant, if desired. The low Btu. gas obtained in separation zone 22 can be passed through line 28 into and through flow path 29 of indirect heat exchanger 14 wherein the'low B.t.u. gas is passed in indirect heat exchanging relationship with additional natural gas passing through flow path 12. The thus warmed low B.t.u. gas passing from flow path 29 can be withdrawn from the system by way of line 31. A valve 32 can be positioned in line 31 and manipulated by pressure recorder controller 33 to maintain the pressure of the fluid in line 31 upstream of valve 32 substantially constant, if desired. The residue gas obtained in separation zone 22 can be passed through line 34 into and through flow path 35 of indirect heat exchanger 14 wherein the residue gas is passed in indirect heat exchanging relationship with additional natural gas passing through flow path 12. The thus warmed residue gas passes from flow path 35 into line 36 and can be withdrawn from the system. A valve 37 can be positioned in line 36 and manipulated by a pressure recorder controller 38 to maintain the pressure of the fluid in line 36 upstream of valve 37 substantially constant, if desired.

The liquid in liquid gas separator 18 is withdrawn therefrom by way of line 41. A throttle valve 42 is positioned in line 41 to efiect a reduction in the pressure of the liquid passing through line 41 and thus a further cooling of such liquid. If desired throttle valve 42 can be manipulated by a liquid level controller 46 to maintain the liquid level in liquid gas separator 18 substantially constant. When the liquid passes through throttle valve 42,

flashing occurs resulting in a two phase fluid downstream of valve 42. This two phase fluid is passed into separation means 43 which is utilized to effect an even distribution of each of the two phases through parallel flow paths 44 and 45 of heat exchanger 15. The vapor phase is withdrawn from separator 43 by way of flow path 46 and introduced into flow paths 44 and 45 while the liquid is withdrawn from phase separator 43 and introduced into flow paths 44 and 45 by means of flow path 47. The introduction of the two phase fluid into flow paths 44 and 45 is in such a manner that the amount of liquid passing into each of flow paths 44 and 45 is substantially the same, and similarly the amount of vapor passing through each of flow paths 44 and 45 is substantially the same. The efliucnt from flow paths 44 and 45 is collected and with drawn from the system by way of line 49. A valve 51 can be positioned in line 49 and manipulated by a pressure recorder controller 52 to maintain the pressure in line 49 upstream of valve 51 substantially constant, if desired. The flow conditions through flow paths 44 and 45 are such that substantially all of the liquid passing therethrough is vaporized by the transfer of heat thereto from the natural gas feed stream passing through flow path 13. By this transfer of heat the natural gas is substantially cooled and/ or partially liquefied depending upon the conditions of temperature and pressure imposed on the system.

Referring now to FIGURE 2, indirect heat exchanger 15 is exemplified as being a shell and tube heat exchanger of the wound bundle type having a cylindrical shell 61 and vessel heads or closure means 62 and 63. A tube bundle comprising a plurality of tubes 13 helically wrapped or coiled around hollow core member 60 is positioned within and substantially coaxial with shell 61. Tube sheets 64 and 65 are positioned within shell 61 and substantially perpendicular to the axis of shell 61. Core member 60 passes through the center of each of tube sheets 64 and 65. Head or closure means 66 is connected to tube sheet 65 to form a feed distribution chamber 67 which is in fluid communication with the internal passages of tubes 13. Head or closure means 68 is connected to tube sheet 64 to form a second chamber 69. Tubes 13 are connected to tube sheets 64 and 65 to provide a plurality of flow paths for fluid communication between chambers 67 and 69. Feed gas passes through conduit 11 into chamber 67 and then into and through tubes 13 into chamber 69. The cooled feed gas is withdrawn from chamber 69 by way 4 of the passageway 71 through hollow core means 60 and passes into conduit 16.

The two phase fluid in conduit 41 is introduced into phase separation chamber 43 which is located in the upper portion of heat exchanger 15. Chamber 43 is the space bounded by closure means 62, vertical cylindrical wall 72, head 68 and an outer or peripherial portion of tube sheet 64. Cylindrical wall 72 is smaller than the inside diameter of shell 61 and is spaced therefrom to form an annular passageway or flow path 46 between chamber 43 and heat exchange chamber 73, that is the interior of that portion of shell 61 containing the tube bundle. The fluid from conduit 41 upon entering chamber 43 separates into a vapor portion and a liquid portion. The vapor portion passes through flow path 46 into chamber 73 while the liquid portion collects in the container formed by wall 72, head 63 and tube sheet 64. The outer portion of tube sheet 64 which forms the bottom of chamber 43 is pro vided with a plurality of openings or passageways 47 to permit the flow of liquid from chamber 43 into chamber 73. The angle from the vertical of flow paths 73 increases from approximately zero at a point near wall 72 to approximately 45 adjacent closure means 68 to provide a spraying of the liquid from chamber 43 onto the tube bundle in such a manner as to effect a substantially even distribution of the liquid among the various paths between tubes 13. The vapor portion will, by its nature, seek to travel through each flow path between tubes 13, and the distribution of vapor among the various flow paths between tubes 13 will be substantially equal as long as the pressure drops are substantially the same. The vapor and vaporized liquid is withdrawn from chamber 73 by way of conduit 49. A liquid seal, such as solder or gasket means, 75 can be provided on the upper surface of the tube bundle adjacent shell 61 to prevent the passage of liquid through the annulus between the tube bundle and shell 61. Referring now to FIGURE 3 there is illustrated a modification of the apparatus of FIGURE 2. Core member 66a can be hollow, but does not provide fluid communication with either chambers 67 or 69. The cooled fluid in chamber 69 is withdrawn therefrom by way of conduits 71a and 16. The two phase fluid in conduit 41 is introduced into a phase separator 43a. Liquid is passed from phase separator 43a by way of conduit 47a into chamber 43b. Chamber 43b is the space bounded by vessel head 62, distribution sheet 64b and shell 61, excluding chamber 69 and its associated tubes and conduit. Instead of a single sheet 47 serving as both a tube sheet and a liquid distribution means, tube sheet 64a is provided for connecting tubes 13 into chamber 69 and a liquid distribution sheet 64b having a plurality of openings 47b there in, is provided for spraying liquid across the upper surface of the tube bundle. The vapor from separator 43:! is passed by way of one or more conduits 46a into shell 61 below plate 64b and above the main portion of the tube bundle, that is into chamber 73. As openings 47b can be provided in sheet 64b in the area between individual tubes 13, such openings 47b can all be substantially perpendicular to the plane of sheet 64b. However, if desired, some or all of openings or passageways 47b can be included at suitable angles to the vertical to provide a more uniform distribution of liquid among the flow paths between tubes 13. The liquid level in chambers 43 and 43b would be self regulating, that is, as the level increases the pressure head increases resulting in an increased flow through openings 47 or 47b.

' EXAMPLE A heat exchanger of the type illustrated in FIGURE 2 is utilized in the refrigeration separation system of FIG- URE 1 with the conditions set forth in Table I.

The resulting heat transfer rate between the mixture of vapors and liquid from line 41 and the feed stream in tubes 13 is considerably better in comparison to a system wherein there is a maldistribution of the liquid and vapor of any consequence.

Table 1 Composition, M01 percent Temper- Component attire, Pressure, Flow,

- F. p.s.i.a. lbs/hr. H6 N C1 0, Ca 04 C5 Reasonable variation and modification are possible withchamber; a second head connected to the upper side of in the scope of the foregoing disclosure, the drawing and 20 said upper tube sheet to form a second chamber; a pluralthe appended claims to the invention. 1 ity of tubes helically wound around said core member and I claim: connected between said upper and lower tube sheets 1. Heat exchanging apparatus comprising a housing through said liquid distribution plate and in fluid comhaving a substantially cylindrical casing, an upper closure rnunication with said first and second chambers; a first member and a lower closure member; ahollow core mem- 25 conduit passing through said housing and connected to her positioned inside of and substantially coaxial with said secondhead to provide fluid communication between said casing; an upper tube sheet and a lower tube sheet said second chamber and said first conduit; a second conpositioned inside of said casing and substantially perpenduit passing through said housing and said first head to dicular to the axis of said casing and connected to said provide fiuid communication with said first chamber; a core member, said core member passing through the phase separator; a third conduit connected to the inlet of center of each of said upper and lower tube sheets; said said phase separator for introducing a two phase fluid upper tube sheet having a first inner portion and a second therein; a fourth conduit connected between a lower porouter portion; a first head connected to the lower side of tion of said phase separator and said housing at a point said lower tube sheet to form a first chamber; a second above said liquid distribution plate for passing liquid into head connected to the upper side of said first portion of the space above said liquid distribution plate and within said upper tube sheet to form a second chamber; a plural said housing; a fifth conduit connected between an upity of tubes helically wound around said core member per portion of said phase separator and said housing at a and connected between said upper and lower tube sheets point below and adjacent to said liquid distribution plate; and in fluid communication with said first and second and a sixth conduit communicating with a lower portion chambers; a first conduit passing through said housing and of said housing for the withdrawal of the two phase fluid connected to the lower end of said core member, the upafter it hasbeen passed in contact with said plurality of per end of said core member being connected to said uptubes. per tube sheet to provide fiuid communication between 3. Apparatus for utilizing a high pressure liquid stream said second chamber and said first conduit; a second conas a cooling fluid in a'heat exchanger having a plurality duit passing through said housing and said first head to of flow paths therethrough and wherein it is desirable that provide fluid communication with said first chamber; a substantially all of the cooling fluid be vaporized in passvertical wall member positioned above said upper tube ing through said heat exchanger although said liquid sheet and connected to the periphery of said upper tube steam is at a pressure higher than the pressure at which sheet; said wall member being spaced from said housing substantially all of said liquid stream would be vaporized to form an annular passageway therebetween; said upper by being passed through said heat exchanger, and wheretube sheet having a plurality of openings therethrough in in said liquid stream would have a liquid phase and a gas said outer portion, the angle from the vertical of said phase upon the pressure of said liquid stream being replurality of openings being greater adjacent said second duced to said pressure at which substantially all of said head than adjacent said wall member; a third conduit liquid stream would be vaporized by being passed through passing through an upper portion of said housing for passsaid heat exchanger, comprising means for reducing the ing a two phase fluid into the space above said upper tube Pressure on Said liquid stream to Said PresiDre at which sheet and Within said wall member; and a fourth c duit substantially all of said liquid stream would be vaporized communicating with a lower portion of said housing for y being passed through said heat exchanger, thereby p the withdrawal of the two phase fluid after it has been ducing a two phase fluid; a heatcxchangerhousins having passed in ontact with said plurality f t b a substantially cylindrical casing, an upper closure mem- 2. Heat exchanging apparatus comprising a housing ber and a lower closure member; a core member posihaving a substantially cylindrical casing, an upper lo tioned inside of and substantially coaxial with said casing; member and a lower closure member; a core member posian pp tube Sheet and a lower tube Sheet Positioned tioned inside of and substantially coaxial with said casing; Side O Said a g d su stantially perpendicular to the an upper tube Sheet, a li uid di tributi plate d a l axis of said casing and connected to said core member, or tube sheet positioned inside of said casing and substansaid core member passing through the center of a h of tially perpendicular to the axis of said casing and con- Said pp and lower tube Sheets; Said pp tube sheet nected to said core member; said liquid distribution plate a n a fi inner p n and a second outer p being between said upper tube she t nd id l w t b a first head connected to the lower side of said lower tube sheet and having a diameter equal to the inside diameter Sheet form a first chamber; a Second head C Hn d of said casing, the diameter of said upper and lower tube Pil Side Of Said first POIfiOH 0f Said uppe t sheets being substantially less than said inside diameter Sheet to form a Second Chamber; p l y Of tubes C of said casing; said liquid distribution plate having a nected between said upper and lower tube sheets and in plurality of openings therethrough; a first head connected fluid communication with said first and second chambers; to the lower side of said lower tube sheet to form a first a first conduit passing through said housing and connected in fluid communication with said second chamber; a second conduit passing through said housing and connected in fluid communication with said first chamber; a vertical wall member positioned above said upper tube sheet and connected to the periphery of said upper tube sheet; said wall member being spaced from said housing to form an annular passageway therebetween; said upper tube sheet having a plurality of openings therethrough in said outer portion; a third conduit passing through an upper portion of said housing for passing said two phase fluid into the space above said upper tube sheet and within said wall member; and a fourth conduit communicating with a lower portion of said housing for the withdrawal of the two phase fluid after it has been passed in contact with said plurality of tubes.

4. Apparatus for utilizing a high pressure liquid stream as a cooling fluid in a heat exchanger having a plurality of flow paths therethrough and wherein it is desirable that substantially all of the cooling fluid be vaporized in passing through said heat exchanger although said liquid stream is at a pressure higher than the pressure at which substantially all of said liquid stream would be vaporized by being passed through said heat exchanger, and wherein said liquid stream would have a liquid phase and a gas phase upon the pressure of said liquid stream being reduced to said pressure at which substantially all of said liquid stream would be vaporized by being passed through said heat exchanger, comprising means for reducing the pressure on said liquid stream to said pressure at which substantially all of said liquid stream would be vaporized by being passed through said heat exchanger, thereby producing a two phase fluid; a heat exchanger housing having a substantially cylindrical casing, an upper closure member and a lower closure member; a core member positioned inside of and substantially coaxial with said casing; an upper tube sheet, a liquid distribution plate and a lower tube sheet positioned inside of said casing and substantially perpendicular to the axis of said casing and connected to said core member; said liquid distribution plate being between said upper tube sheet and said lower tube sheet and having a diameter equal to the inside diameter of said casing; the diameter of said upper and lower tube sheets being substantially less than said inside diameter of said casing; a first head connected to the lower side of said lower tube sheet to form a first chamber; a second head connected to the upper side of said upper tube sheet to form a second chamber; a plurality of tubes connected between said upper and lower tube sheets through said liquid distribution plate and in fluid communication with said first and second chambers; a first conduit passing through said housing and connected to said second head to provide fluid communication between said second chamber and said first conduit; 21 second conduit passing through said housing and said first head to provide fluid communication with said first chamber; said liquid distribution plate having a plurality of openings therethrough; a phase separator; a third conduit connected to the inlet of said phase separator for introducing said two phase fluid therein; a fourth conduit connected be tween a lower portion of said phase separator and said housing at a point above said liquid distribution plate for passing liquid into the space above said liquid distribution plate and within said housing; a fifth conduit connected between an upper portion of said phase separator and said housing at a point below and adjacent to said liquid distribution plate; and a sixth conduit communicating with a lower portion of said housing for the withdrawal of the two phase fluid after it has been passed in contact with said plurality of tubes.

5. Heat exchanging apparatus comprising a housing having a substantially cylindrical casing, an upper closure member and a lower closure member; an upper tube sheet and a lower tube sheet positioned inside of said casing and substantially perpendicular to the axis of said casing; 21 first head connected to the lower side of said lower tube sheet to form a first chamber; a second head connected to the upper side of said upper tube sheet to form a second chamber; a plurality of tubes connected between said upper and lower tube sheets and in fluid communication with said first and second chambers; a first conduit means passing through said housing to provide fluid communication between said second chamber and said first conduit means; a second conduit means passing through said housing to provide fluid communication between said first chamber and said second conduit means; means for separating a two phase fluid into a liquid portion and a vapor portion; means for passing said vapor portion downwardly in said housing and in substantially equal heat exchanging relationship with each of said plurality of tubes, means adjacent said upper tube sheet for spraying said liquid portion against said plurality of tubes in substantially equal heat exchanging relationship with each of said plurality of tubes, and third conduit means connected to a lower portion of said housing for withdrawing therefrom the two phase fluid after it has been passed in contact with said plurality of tubes.

References Cited in the file of this patent UNITED STATES PATENTS 2,561,506 Garretson July 24, 1951 3,004,901 Nerge et al Oct. 17, 1961 3,050,377 Christensen Aug. 21, 1962 

5. HEAT EXCHANGING APPARATUS COMPRISING A HOUSING HAVING A SUBSTANTIALLY CYLINDRICAL CASING, AN UPPER CLOSURE MEMBER AND A LOWER CLOSURE MEMBER; AN UPPER TUBE SHEET AND A LOWER TUBE SHEET POSITIONED INSIDE OF SAID CASING AND SUBSTANTIALLY PERPENDICULAR TO THE AXIS OF SAID CASING; A FIRST HEAD CONNECTED TO THE LOWER SIDE OF SAID LOWER TUBE SHEET TO FORM A FIRST CHAMBER; A SECOND HEAD CONNECTED TO THE UPPER SIDE OF SAID UPPER TUBE SHEET TO FORM A SECOND CHAMBER; A PLURALITY OF TUBES CONNECTED BETWEEN SAID UPPER AND LOWER TUBE SHEETS AND IN FLUID COMMUNICATION WITH SAID FIRST AND SECOND CHAMBERS; A FIRST CONDUIT MEANS PASSING THROUGH SAID HOUSING TO PROVIDE FLUID COMMUNICATION BETWEEN SAID SECOND CHAMBER AND SAID FIRST CONDUIT MEANS; A SECOND CONDUIT MEANS PASSING THROUGH SAID HOUSING TO PROVIDE FLUID COMMUNICATION BETWEEN SAID FIRST CHAMBER AND SAID SECOND CONDUIT MEANS; MEANS FOR SEPARATING A TWO PHASE FLUID INTO A LIQUID PORTION AND A VAPOR PORTION; MEANS FOR PASSING SAID VAPOR PORTION DOWNWARDLY IN SAID HOUSING AND IN SUBSTANTIALLY EQUAL HEAT EXCHANGING RELATIONSHIP WITH EACH OF SAID PLURALITY OF TUBES, MEANS ADJACENT SAID UPPER TUBE SHEET FOR SPRAYING SAID LIQUID PORTION AGAINST SAID PLURALITY OF TUBES IN SUBSTANTIALLY EQUAL HEAT EXCHANGING RELATIONSHIP WITH EACH OF SAID PLURALITY OF TUBES, AND THIRD CONDUIT MEANS CONNECTED TO A LOWER PORTION OF SAID HOUSING FOR WITHDRAWING THEREFROM THE TWO PHASE FLUID AFTER IT HAS BEEN PASSED IN CONTACT WITH SAID PLURALITY OF TUBES. 